Drill bits



Aug. 25, 1959 E7 6. BOICE ETAL DRILL BITS 4 Sheets-Sheet 1 Original Filed Dec. 10. 195] INVENTORS wwa;

1959 E. s. BOICE ETAL 2,901,224

DRILL BITS 4 Sheets-Sheet 2 Original Filed Dec. 10. 195] f/v/n 6. 50/0@ Robe/i 6. Pefer INVENTORS Mm Aug. 25, 1959 V E. G. BOICE ETAL 2,901,224

DRILL BITS Original Filed Dec. 10. 1951 4 Shets-Sheet s Ruben 6.

INVENTORJ 2M KM E. G. BOICE EI'AL Aug. 25, 1959 DRILL BITS 4 Sheets-Sheet 4 ox iginal Filed Dec 10, 1951 INVENTORJ BY flwjwm A TTORNEVJ United States Patent DRILL. BITS- Elvin G. Boice and Robert Peter, Houston, Tex., as-

signors to Reed Roller Bit Company, Houston, Tex., a corporation of Texas 3 Claims. (crass-s49 This invention relates to new and useful improvements in drill bits.

This application is a division of ouricopending U.S. patent application, Serial No. 260,858, filed December 10, 1951, now Patent No. 2,728,559.,

A general object of this invention is to provide a new and improved drill bit cutter.

A specific object of this invention is to provide a drill bit having a cutter which is formed with herringbone-type teeth which increases the bottom hole coverage, the inner row of said cutter teeth being Widely spaced and directed in a manner to provide for smoother rolling of the cutter while still providing good impact with the formation and efficient cutting action; the arrangement of the herringbone design facilitating manufacture of the cutter by eliminating. the usual annular groove between cutter: teeth which was required because of the mechanical limitations of the available milling equipment.

Other objects will appear hereinafter.

Figure 1. is anelevation of a two cutter bit, constructed in accordance with the invention;

Figure 2 is a bottom view thereof,

Figure 3 is. an enlarged vertical, sectional view of the bit; t

Figure. '4 is. a partial sectional view with the cutters removed front the spindles; h

Figure 5 is. a bottom view of the parts illustrated in Figure 4, taken on the section line of Figure. 4;.

Figure 6 is. a perspective view ofthe cutter, having herringbone-typeteethfand T v 1 Figure 7 is a schematic view'illust'rating the manner of forming the cutter teeth of the cutter of Figure 6 by the usual milling tool.

In the drawings, the numeral 10 designates a bit body having the usual upwardly extending, externally threaded pin 11, preferably made integral therewith. A bore 12 extends through the bit body and pin, and the usual circulation ports 13 extend from its lower end. The bit body and pin may be made in two halves or sections which are fitted together along the line Z and properly welded in the usual manner as indicated at 50.

Depending legs 15 extend downwardly from. the bit body in diametrically opposed relationship to each other and spindle shafts or journals 16 and 17 each have their outer ends supported within the legs 15. A short or side cutter A is adapted to be rotatably mounted on the shaft 16 while a long or cross roller B is arranged to mount on the shaft 17. The rollers are supported on suitable roller bearings 18 and ball bearings 19 in any suitable manner.

The particular mounting of the spindle shafts 16 and 17 with respect to each other is clearly illustrated in Figures 3 and 4. The shaft 16 has a reduced cylindrical portion 20 which engages within an opening 21 in one of the supporting legs 15 and is Welded to the leg as indicated at 22. The longitudinal axis of the spindle or shaft 16 is disposed at a predetermined angle with respect to a horizontal plane and in actual practice this angle, in-

di'cated at C in Figure 3, is approximately The inner end of the shaft or spindle 16 is formed with an extension 23, which when the shaft is in place on the bit body is disposed at substantially the axial center of the bit.

The shaft 17 has a reduced cylindrical extension 24 at its outer end engageable within an opening 25 in the opposite leg of the bit, and said reduced portion is welded as indicated at 26 to said supporting leg. The shaft 17 is also disposed at an angle from a horizontal plane, and this angle indicated at D in Figure 3, is greater than the angle C at which the shaft 16 is disposed; in actual practice, the angle D is 33. In addition to the angle of the shaft 17 being different than the angle of the shaft 16, the shaft 17 is raised vertically in a slightly higher plane than is the shaft 16 whereby the intersection of the center line B of the shaft 17 with the outer surface of its supporting legis in a higher horizontal plane E than the plane F in which the intersection of the axis F of shaft 16 with the outer surface of its leg is located. The difference in this offset is clearly shown by the space G and by so offsetting the shafts, the axes E and F of the two shafts do: not intersect at the axis or center line H of the bit body.

The inner end of the shaft 1'7 has a reduced cylindrical shank 27 which is adapted to engage an opening 28 in the extension 23 on the shaft 16 and the inner ends of the two shafts are connected by suitable welding 29'. By forming the extension on the shaft 16 and by connecting the inner end of the shaft 17' thereto, the necessity for providing a separate bridge element is eliminated which simplifies the construction of'th'e bit.

The short or side cutter A is mounted on the shaft 16 and its construction is illustrated in Figure 6. The cutter is formed with an outer row of cutter teeth 30 and an inner row of cutter teeth 31 which are arranged in a herringbone pattern. It has been found that the angle of, disposition of the herringbone teeth 34) and 31 is preferably at approximately 45 with respect to the axis of the cutter, although the invention is not to be limited to thisparticular angle since some variation may occur. By arranging the teeth 30 and 31 in herringbone pattern the necessity for an annular groove-in the external surface of the cutter between the teeth is eliminated. Referring to Figure 7, where'thedotted circles represent the milling cutter it will be seen that the teeth 30 and 31 may be formed without leaving any annular groove about the external surface of the cutter. In prior tooth arrangements, the annular groove was required to overcome the mechanical limitations of available milling equipment. Obviously, by eliminating such groove the bottom hole coverage of the cutter is increased. Further the herringbone pattern of tooth construction has been found to provide for smoother operation without sacrificing cutting efficiency.

In addition to the herringbone pattern the inner row of teeth 31 is of the cantilever type, that is, the end of each tooth projects outwardly beyond the plane of the end 16a of the cutter. In prior practice, it has been usual to terminate the teeth in the plane indicated by the dotted line L in Figure 3, that is, the cutter teeth terminated in the same plane as the inner face 16a of the shaft 16. By extending the teeth in the manner shown it will be evident that an increased tooth contact with the formation will be produced. a

The cutter B is illustrated in Figures 1 and 2 and includes an outer row of teeth 32 and an inner row of teeth 33. Each tooth of the outer row 32 is substantially straight or With its cutting edge in a longitudinal plane parallel to the axis of the cutter while each tooth of the inner row 33 is disposed on a helix or spiral. Each tooth of the inner row of teeth 33 is of the cantilever type and the extended end thereof is arranged to overlap the inner teeth 31 of the cutter A as is clearly illustrated in Figure 3. Since the inner end of each tooth 33 extends beyond the end face 170 of the cutter B, the extension 23 on'the shaft '16 is recessed as shown at 234: to accommodate the same. Ordinarily, the teeth 33-have been terminated along the dotted line T in Figure 3 and by extending the teeth in the manner illustrated, an increased cutting area is provided.

By disposing the spindles in the manner hereinabove described and constructing the cutters A and B to provide for the overlapping of the inner teeth 31 of cutter A with the cutter B and the extension of the inner teeth 33 on the cutter B, the cutting zone or area of the cutters is increased to provide for a more efficient drilling operation. As indicated in Figure 3 the spacing between the cutter ends is indicated by the arrow J; if the cutters are made in a normal manner without the ends of the teeth being extended in the manner hereinbefore described, the spacing would be as shown by the arrow K in Figure 3, and it is therefore evident that the amount of formation whichis not contacted by the bit is materially reduced. This provides for increased drilling efliciency and better cutting action.

The disposition of the spindles 16 and 17 not only makes it possible to provide cutters having increased contact area with the formation but also makes possible the proper support of the inner ends of the spindles without the necessity of a separate bridge element. The extension' 23 which is formed on the shaft 16 functions as the bridge and provides an arrangement whereby thetwo spindles or shafts may be securely anchored to each other to properly support the same. In addition to providing amplified cutting area, the particular arrangement minimizes the exposure of non-cutting elements to the bottom of the hole, since the space at the central portion of the bore is materially reduced.

From the foregoing, it will be evident that a two cutter bit having a maximum contact with the formation is provided. The cutters A and B, being formed with cantilever-type inner teeth overlap and interengage to increase the contact area; in addition the provision of the herringbone pattern on the cutter not only facilitates the manufacture of the cutter but also increases the'cutting area of said cutter.

y We claim:

v 1. As a sub-combination in a roller bit, a roller cutter comprising an annular body, an outer row'of cutter teeth on the body, and an inner row of cutter teeth on the body, said outer and inner rows of teeth being disposed in a herringbone pattern, thejteeth in one row being staggered relative to the teeth in the other row with the adjacent portions of the said rows of teeth overlapping each other, each tooth of the inner row being disposed at an inclination of approximately forty five degrees in one direction from the axis of the cutter body and each tooth of the outer row being disposed at an inclination in an opposite direction from the axis of the cutter body also at an inclination of approximately forty five degrees.

2. A roller cutter for a roller bit including, an annular cutter body, a first set of cutter teeth on said body,

all of said teeth in said first set being disposed at the same angle with respect to the axis of said cutter body, and a second set of cutter-teeth on said body spaced from said first set of cutter teeth, said first and second sets of teeth being disposed to provide a herringbone pattern,

the teeth in one set being staggered relative to the teeth in the other set, the adjacent portions of said sets of teeth overlapping each other, all of said teeth in said second set being disposed at an angle with respect to the axis of said cutter body which is opposite to the angle of the teeth of said first set. i

p 3 A roller cutter for a roller bit including, an annular cutter body, a first set of cutter teeth on said body,- all of said teeth in said first set being disposed'at-the same angle with respect to the axis of said cutter body,

and a second set of cutter teeth on said body spaced from said first set of cutter teeth, all of said teeth in said second set being disposed at an angle with respect to the axis of said cutter body which is opposite to the angle of the teeth of said first set, the teeth of saidfirst set being alternately positioned on said body. andstaggered with respect to the teeth of said second set, the adjacent portions of the said sets of teeth overlapping each other.

References Cited in the file of this patent UNITED STATES PATENTS Boice Sept. 27, 1955 

